Radio terminal apparatus and its reception control program

ABSTRACT

A base station transmits information in a downlink signal that identifies whether the base station is an adaptive array base station. If a terminal capable of performing diversity reception determines that a terminal to be connected is an adaptive array base station, it stops to perform diversity reception and set an antenna used for an uplink signal transmission to be used for an immediately following reception among a plurality of antennas ( 11, 12 ). Thus, a reception effectively utilizing transmission directivity from the adaptive array base station is attained, and interference wave can be reduced. These process are executed with software by DSP ( 18 ).

TECHNICAL FIELD

[0001] The present invention relates to a radio terminal apparatus and areception operation control program thereof, and specifically, to aradio terminal apparatus that selects the type of a reception operationin accordance with the type of a radio base station to be connected, anda reception operation control program for controlling such an operation.

BACKGROUND ART

[0002] Recently, in a mobile communication system (e.g., PersonalHandyphone System: hereinafter referred to as PHS) that has beendeveloping rapidly, PDMA (Path Division Multiple Access) scheme isproposed, which can connect radio terminal apparatuses (terminals) of aplurality of users to a radio base station (base station) in a spatialmultiplexing manner, by spatially dividing an identical time slot of anidentical frequency for improving the frequency effectiveness of a radiowave.

[0003] In this PDMA scheme, an adaptive array technique is currentlyemployed, in which an uplink signal from each user's terminal antenna isreceived by an array antenna of a base station and extracted withreception directivity through an adaptive array process. A downlinksignal to the terminal from the base station is transmitted from thearray antenna with transmission directivity to the antenna of theterminal.

[0004] Such an adaptive array process is well known in the art anddescribed in detail, for example, in “Chapter 3: MMSE Adaptive Array” in“Adaptive Signal Processing by Array Antenna”, Nobuyoshi Kikuma, KagakuGijutsu Shuppan, pp. 35-49. Thus, description on its operation principleis not given herein. Further, specific arrangement of a radio apparatusemploying the adaptive array processing is well known in the art, asdisclosed in detail in International Publication No. WO00/79702 of thepresent applicant.

[0005] In the following, a base station that performs downlinktransmission directivity control using such an adaptive array process isreferred to as an adaptive array base station.

[0006] As for a terminal, one performing selective diversity reception(hereinafter referred to as diversity reception) using a plurality ofantennas is known. In reception, such a terminal operates to select oneantenna with higher reception level as a reception antenna from, forexample, two antennas. Such a conventional diversity reception terminalperforms the above mentioned diversity reception regardless of whetherthe base station to be connected is an adaptive array base stationperforming transmission directivity control or a non-directivity basestation.

[0007]FIGS. 8A and 8B schematically shows the connection state betweenterminals and adaptive array base stations, FIG. 8A showing theconnection state between terminals not performing diversity receptionand adaptive array base stations, and FIG. 8B showing the connectionstate between terminals performing diversity reception and adaptivearray base stations.

[0008] Referring to FIG. 8A, as indicated by a bold arrow, a terminal 3not performing diversity reception is connected to a desired adaptivearray base station 1, and from an array antenna of adaptive array basestation 1, a downlink signal is transmitted with transmissiondirectivity to one antenna of terminal 3 that has transmitted an uplinksignal. A hatched region D (D: Desired) indicates a state where a beamof signal wave is directed to terminal 3 from adaptive array basestation 1.

[0009] In this case, terminal 3 can receive the downlink signal fromadaptive array base station 1 at the maximum power due to thetransmission directivity of desired adaptive array base station 1. Therelationship between a terminal 4 not performing diversity reception andits desired adaptive array base station 2 is the same.

[0010] Though the signal wave from adaptive array base station 2 asindicated by a broken arrow U (U: Undesired) functions as aninterference wave for terminal 3, as can be seen from the emission stateof the signal wave in FIG. 8A, the signal power of the interference wavefrom adaptive array base station 2 received at terminal 3 is of theminimum. The relationship between terminal 4 not performing diversityreception and its non-desired adaptive array base station 1 is the same.

[0011] As above, an excellent connection state with less interferencecan be realized between a terminal not performing diversity receptionand a desired adaptive array base station.

[0012] On the other hand, referring to FIG. 8B, for example a terminal 5performing diversity reception transmits an uplink signal from oneantenna 5 a, establishing a connection relationship with adaptive arraybase station 1 as indicated by a bold arrow, similarly to therelationship shown in FIG. 8A. Hence, at antenna 5 a of terminal 5, adownlink signal from desired adaptive array base station 1 is receivedat the maximum power, while a transmission signal from a non-desiredadaptive array base station 2 (an interference wave) indicated by abroken (fine) arrow is received at the minimum power.

[0013] Since beam of signal wave D from desired adaptive array basestation 1 is not directed to the other antenna 5 b of terminal 5 nottransmitting an uplink signal, the power of reception signal fromadaptive array base station 1 decreases. Therefore, the power ofinterference wave U from non-desired adaptive array base station 2indicated by a broken (bold) arrow relatively increases at antenna 5 b.

[0014] The similar state occurs at antennas 6 a and 6 b of a terminal 6performing diversity reception in the relationship with adaptive arraybase stations 1 and 2.

[0015] The similar problem arises in a spatial multiplexing base stationrealizing spatial multiple connection using such an adaptive arrayprocess. FIGS. 9A and 9B schematically indicate the connecting statebetween terminals and base stations, FIG. 9A showing connection statebetween terminals not performing diversity reception and a spatialmultiplexing base station, FIG. 9B showing connection state betweenterminals performing diversity reception and a spatial multiplexing basestation.

[0016] Referring to FIG. 9A, as indicated by a bold arrow, terminals 30and 40 not performing diversity reception are connected in spatialmultiplexing manner to a desired base station 10 through the adaptivearray process, and from an array antenna of spatial multiplexing basestation 10, a downlink signal is transmitted with transmissiondirectivity to one antenna of each of terminals 30 and 40 that hastransmitted an uplink signal. A hatched region D indicates a state wherea beam of signal wave is directed to each of terminals 30 and 40 fromspatial multiplexing base station 10.

[0017] In this case, terminals 30 and 40 each can receive the downlinksignal from base station 10 at the maximum power due to the transmissiondirectivity of the desired base station 10.

[0018] As above, an excellent connection state with less interferencecan be realized between a terminal not performing diversity receptionand a desired spatial multiplexing base station.

[0019] On the other hand, referring to FIG. 9B, for example a terminal50 performing diversity reception transmits an uplink signal from oneantenna 50 a, establishing a connection relationship with spatialmultiplexing base station 10 as indicated by a bold arrow, similarly tothe relationship shown in FIG. 9A. Hence, at antenna 50 a of terminal50, a downlink signal from desired spatial multiplexing base station 10is received at the maximum power.

[0020] Since beam of signal wave D from desired spatial multiplexingbase station 10 is not directed to the other antenna 50 b of terminal 50not transmitting an uplink signal, the power of reception signal U fromspatial multiplexing base station 10 decreases. Therefore, the power ofinterference wave from a non-desired base station that is not shownrelatively increases at antenna 50 b.

[0021] The similar state occurs for antennas 60 a and 60 b of a terminal60 performing diversity reception.

[0022] As above, at a terminal performing diversity reception,regardless of whether a desired base station is an adaptive array basestation controlling downlink transmission directivity, one antenna withhigher reception level is selected from two antennas as a receptionantenna. Therefore, for example in a terminal 5 of FIG. 8B, when acombined power of a low reception power from desired adaptive array basestation 1 and a large interference wave U from non-desired adaptivearray base station 2 received at antenna 5 b not transmitting an uplinksignal exceeds the reception power from a desired adaptive array basestation 1 received at antenna 5 a that has transmitted an uplink signal,antenna 5 b is selected as a reception antenna.

[0023] In this case, the signal received at antenna 5 b has a largepower of interference wave U from non-desired adaptive array basestation 2 relative to the downlink reception signal from desiredadaptive array base station 1, and hence it is a signal with a largeinterference component, i.e., a signal with low so-called DU ratio(Desired user's power: Undesired user's power).

[0024] Even when an attempt is made to demodulate such a receptionsignal with low DU ratio at terminal 5, an error occurs in a frame of ademodulation signal and a correct demodulation fails. In special, whenthe power level of a downlink signal (interference wave) U fromnon-desired adaptive array base station 2 increases, in the worst case,terminal 5 may inappropriately demodulate a downlink signal that istransmitted to another user's terminal 6 from adaptive array basestation 2.

[0025] Similar problem arises in the spatial multiplexing base stationsshown in FIGS. 9A and 9B.

[0026] Thus, in the conventional mobile communication system, when aterminal that performs diversity reception is connected to an adaptivearray base station (or a spatial multiplexing base station), the DUratio at the terminal decreases, and its reception performance isdegraded by an interference wave. Accordingly, there exist a problemthat the effect of the adaptive array technique to reduce the frequencyreuse distance (the minimum distance between base stations that canshare the same frequency) is reduced.

[0027] Therefore, the object of the present invention is to provide aradio terminal apparatus in which the reception performance is notdegraded even when connected to a base station that controls downlinktransmission directivity, such as an adaptive array base station or aspatial multiplexing base station, by selecting the reception operationtype of the terminal in accordance with the type of the base station tobe connected, and to provide a reception operation controlling programthereof.

DISCLOSURE OF THE INVENTION

[0028] One aspect of the present invention is a radio terminal apparatusin a mobile communication system, and the mobile communication systemincludes a plurality of radio base stations. Each of the plurality ofradio base stations transmits a signal containing information thatidentifies a type of the radio base station. The radio terminalapparatus includes determination means for receiving a signal from aradio base station to be connected among the plurality of radio basestations and determining a type of the radio base station based on theinformation, and selection means for selecting a reception operationmode for receiving a signal from the radio base station in accordancewith the determined type of the radio base station.

[0029] Another aspect of the present invention is a radio terminalapparatus capable of performing diversity reception using a plurality ofantennas in a mobile communication system, and the mobile communicationsystem includes a plurality of radio base stations. Each of theplurality of radio base stations transmits information that identifieswhether the radio base station is a radio base station performing anadaptive array operation with directivity. The radio terminal apparatusincludes determination means for receiving a signal from a radio basestation to be connected among the plurality of radio base stations anddetermining whether the radio base station is a radio base stationperforming the adaptive array operation based on the information, andset means for setting an antenna used for a signal transmission to theradio base station among the plurality of antennas to be used for asignal reception from the radio base station that immediately followsthe signal transmission when the radio base station is determined to bea radio base station performing the adaptive array operation, and forsetting the plurality of antennas to be used for receiving a signal fromthe radio base station by diversity reception when the radio basestation is determined to be a radio base station not performing theadaptive array operation.

[0030] Still another aspect of the present invention is a radio terminalapparatus capable of selectively performing adaptive array reception ordiversity reception using a plurality of antennas in a mobilecommunication system, and the mobile communication system includes aplurality of radio base stations. Each of the plurality of radio basestations transmits information that identifies whether the radio basestation is a radio base station performing an adaptive array operationwith directivity. The radio terminal apparatus includes determinationmeans for receiving a signal from a radio base station to be connectedamong the plurality of radio base stations, and determining whether theradio base station is a radio base station performing the adaptive arrayoperation based on the information, and set means for setting theplurality of antennas to be used for receiving a signal from the radiobase station by adaptive array reception when the radio base station isdetermined to be a radio base station performing the adaptive arrayoperation, and for setting the plurality of antennas to be used forreceiving a signal from the radio base station by diversity reception oradaptive array reception when the radio base station is determined to bea radio base station not performing the adaptive array operation.

[0031] Still another aspect of the present invention is a radio terminalapparatus capable of performing diversity reception using a plurality ofantennas in a mobile communication system, and the mobile communicationsystem includes a plurality of radio base stations. Each of theplurality of radio base stations transmits information that identifieswhether the radio base station is a radio base station performing aspatial multiplexing operation with directivity. The radio terminalapparatus includes determination means for receiving a signal from aradio base station to be connected among the plurality of radio basestations, and determining whether the radio base station is a radio basestation performing the spatial multiplexing operation based on theinformation, and set means for setting an antenna used for a signaltransmission to the radio base station among the plurality of antennasto be used for a signal reception from the radio base station thatimmediately follows the signal transmission when the radio base stationis determined to be a radio base station performing the spatialmultiplexing operation, and for setting the plurality of antennas to beused for receiving a signal from the radio base station by diversityreception when the radio base station is determined to be a radio basestation not performing the spatial multiplexing operation.

[0032] Still another aspect of the present invention is a radio terminalapparatus capable of selectively performing adaptive array reception ordiversity reception using a plurality of antennas in a mobilecommunication system, and the mobile communication system includes aplurality of radio base stations. Each of the plurality of radio basestations transmits information that identifies whether the radio basestation is a radio base station performing a spatial multiplexingoperation with directivity. The radio terminal apparatus includesdetermination means for receiving a signal from a radio base station tobe connected among the plurality of radio base stations, and determiningwhether the radio base station is a radio base station performing thespatial multiplexing operation based on the information, and set meansfor setting the plurality of antennas to be used for receiving a signalfrom the radio base station by adaptive array reception when the radiobase station is determined to be a radio base station performing thespatial multiplexing operation, and for setting the plurality ofantennas to be used for receiving a signal from the radio base stationby diversity reception or adaptive array reception when the radio basestation is determined to be a radio base station not performing thespatial multiplexing operation.

[0033] Still another aspect of the present invention is a receptionoperation control program for controlling a reception operation in aradio terminal apparatus in a mobile communication system, and themobile communication system includes a plurality of radio base stations.Each of the plurality of radio base stations transmits a signalcontaining information that identifies a type of the radio base station.The reception operation control program causes a computer to execute adetermination step of receiving a signal from a radio base station to beconnected among the plurality of radio base stations and determining atype of the radio base station based on the information, and a selectionstep of selecting a reception operation mode for receiving a signal fromthe radio base station in accordance with the determined type of theradio base station.

[0034] Still another aspect of the present invention is a receptionoperation control program for controlling a reception operation in aradio terminal apparatus capable of performing diversity reception usinga plurality of antennas in a mobile communication system, and the mobilecommunication system includes a plurality of radio base stations. Eachof the plurality of radio base stations transmits information thatidentifies whether the radio base station is a radio base stationperforming an adaptive array operation with directivity. The receptionoperation control program causes a computer to execute a determinationstep of receiving a signal from a radio base station to be connectedamong the plurality of radio base stations and determining whether theradio base station is a radio base station performing the adaptive arrayoperation based on the information, and a set step of setting an antennaused for a signal transmission to the radio base station among theplurality of antennas to be used for a signal reception from the radiobase station that immediately follows the signal transmission when theradio base station is determined to be a radio base station performingthe adaptive array operation, and for setting the plurality of antennasto be used for receiving a signal from the radio base station bydiversity reception when the radio base station is determined to be aradio base station not performing the adaptive array operation.

[0035] Still another aspect of the present invention is a receptionoperation control program for controlling a reception operation in aradio terminal apparatus capable of selectively performing adaptivearray reception or diversity reception using a plurality of antennas ina mobile communication system, and the mobile communication systemincludes a plurality of radio base stations. Each of the plurality ofradio base stations transmits information that identifies whether theradio base station is a radio base station performing an adaptive arrayoperation with directivity. The reception operation control programcauses a computer to execute a determination step of receiving a signalfrom a radio base station to be connected among the plurality of radiobase stations and determining whether the radio base station is a radiobase station performing the adaptive array operation based on theinformation, and a set step of setting the plurality of antennas to beused for receiving a signal from the radio base station by adaptivearray reception when the radio base station is determined to be a radiobase station performing the adaptive array operation, and for settingthe plurality of antennas to be used for receiving a signal from theradio base station by diversity reception or adaptive array receptionwhen the radio base station is determined to be a radio base station notperforming the adaptive array operation.

[0036] Still another aspect of the present invention is a receptionoperation control program for controlling a reception operation in aradio terminal apparatus capable of performing diversity reception usinga plurality of antennas in a mobile communication system, and the mobilecommunication system includes a plurality of radio base stations. Eachof the plurality of radio base stations transmits information thatidentifies whether the radio base station is a radio base stationperforming spatial multiplexing operation with directivity. Thereception operation control program causes a computer to execute adetermination step of receiving a signal from a radio base station to beconnected among the plurality of radio base stations and determiningwhether the radio base station is a radio base station performing thespatial multiplexing operation based on the information, and a set stepof setting an antenna used for a signal transmission to the radio basestation among the plurality of antennas to be used for a signalreception from the radio base station that immediately follows thesignal transmission when the radio base station is determined to be aradio base station performing the spatial multiplexing operation, andfor setting the plurality of antennas to be used for receiving a signalfrom the radio base station by diversity reception when the radio basestation is determined to be a radio base station not performing thespatial multiplexing operation.

[0037] Still another aspect of the present invention is a receptionoperation control program for controlling a reception operation in aradio terminal apparatus capable of selectively performing adaptivearray reception or diversity reception using a plurality of antennas ina mobile communication system, and the mobile communication systemincludes a plurality of radio base stations. Each of the plurality ofradio base stations transmits information that identifies whether theradio base station is a radio base station performing a spatialmultiplexing operation with directivity, the reception operation controlprogram causes a computer to execute a determination step of receiving asignal from a radio base station to be connected among the plurality ofradio base stations and determining whether the radio base station is aradio base station performing the spatial multiplexing operation basedon the information, and a set step of setting the plurality of antennasto be used for receiving a signal from the radio base station byadaptive array reception when the radio base station is determined to bea radio base station performing the spatial multiplexing operation, andfor setting the plurality of antennas to be used for receiving a signalfrom the radio base station by diversity reception or adaptive arrayreception when the radio base station is determined to be a radio basestation not performing the spatial multiplexing operation.

[0038] As above, according to the present invention, a radio terminalapparatus can realize optimum reception method corresponding to anoperation type of a radio base station to be connected, by automaticallyselecting a reception operation of the terminal in accordance with atype of the base station to be connected, and degradation of receptionperformance at the terminal can be prevented.

[0039] In special, when a radio base station is an adaptive array basestation or a spatial multiplexing base station, by causing a radioterminal apparatus capable of performing diversity reception to set anantenna used for a transmission to be used for an immediately followingreception, an excellent reception from the radio base station withtransmission directivity can be attained at the radio terminalapparatus, and consequently, reduction of interference component can beattained.

[0040] Further, when a radio base station is an adaptive array basestation or a spatial multiplexing base station, by causing a radioterminal apparatus capable of performing adaptive array reception ordiversity reception to set adaptive array reception, an excellentreception from the radio base station without interference wave can beattained at the radio terminal apparatus, and reduction of interferencecomponent can be attained.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041]FIG. 1 is a conceptual view schematically showing an operationprinciple of a first embodiment of the present invention;

[0042]FIG. 2 is a schematic view showing one example of a frame formatused in the first embodiment of the present invention;

[0043]FIG. 3 is a timing diagram indicating a signaltransmission/reception state between a terminal and a base stationaccording to the first embodiment of the present invention;

[0044]FIG. 4 is a functional block diagram showing a systemconfiguration of a terminal according to the first embodiment of thepresent invention;

[0045]FIG. 5 is a flow chart showing an operation of the terminalaccording to the first embodiment shown in FIG. 4;

[0046]FIG. 6 is a functional block diagram showing a systemconfiguration of a terminal according to a second embodiment of thepresent invention;

[0047]FIG. 7 is a flow chart showing an operation of the terminalaccording to the second embodiment shown in FIG. 6;

[0048]FIGS. 8A and 8B are conceptual views schematically showing anoperation principle of a conventional mobile communication system; and

[0049]FIGS. 9A and 9B are conceptual views schematically showing anotheroperation principle of a conventional mobile communication system.

BEST MODES FOR CARRYING OUT THE INVENTION

[0050] In the following, embodiments of the present invention aredescribed in detail referring to the figures. Throughout the figures,identical or corresponding parts are given the identical referencecharacter, and its description is not repeated.

[0051] [First Embodiment]

[0052]FIG. 1 is a conceptual view schematically showing an operationprinciple of a first embodiment of the present invention, and morespecifically, it illustrates a connection state between terminals thatcan perform diversity reception and adaptive array base stations.

[0053] Referring to FIG. 1, adaptive array stations 1 and 2 are assumedto transmit in a constant cycle identification information indicatingthat they are adaptive array base stations that performs transmissiondirectivity control using, for example, an adaptive array technique.

[0054] Terminals 7 and 8 are terminals that normally performs diversityreception, and when recognizing that the desired base station to beconnected is an adaptive array base station based on the above mentionedidentification information, they stop to perform the selective diversityreception that is based on a reception level as indicated in FIG. 8B,and transit to a reception operation described below.

[0055] In a transmission/reception to/from an adaptive array basestation with transmission directivity, the transmission directivity of adownlink signal from an array antenna of the adaptive array base stationis directed to the antenna of a terminal that has transmitted an uplinksignal.

[0056] Therefore, according to the first embodiment of the presentinvention, when a base station to be connected is recognized to be anadaptive array base station, diversity reception in which a receptionantenna is switched in accordance with reception level is stopped at theterminal, and the antenna selection is controlled to constantly use oneantenna among a plurality of (e.g., two) diversity antennas, which isused for transmitting an uplink signal to the base station in one frame,for receiving a downlink signal from the base station in an immediatelyfollowing frame.

[0057] For instance, in the example of FIG. 1, when terminal 7determines that desired base station 1 is an adaptive array basestation, one antenna 7 a used for transmitting an uplink signal in oneframe is used for receiving a downlink signal from an array antenna ofbase station 1 in an immediately following frame. As a result, the beamof signal wave D is directed to antenna 7 a, establishing an excellentconnection between terminal 7 and base station 1 as indicated by a boldarrow and minimizing the level of interference wave U from non-desiredbase station 2.

[0058] Though not shown, when the uplink signal is transmitted to basestation 1 by the other antenna 7 b, this antenna 7 b is likewise usedfor receiving the downlink signal from base station 1 in an immediatelyfollowing frame, and an excellent connection is established, with thebeam of signal wave D of base station 1 being directed to antenna 7 b.

[0059] The relationship between terminal 8 that can perform diversityreception and its desired adaptive array base station 2 is the same.

[0060]FIG. 2 is a schematic view showing one example of a frame formatused in the first embodiment of the present invention.

[0061] As described above, in the first embodiment of the presentinvention, each base station constituting the mobile communicationsystem transmits in a constant cycle identification informationindicating the type of an operation of the base station, morespecifically, indicating whether the base station is an adaptive arraybase station that performs downlink transmission directivity control.

[0062]FIG. 2 schematically shows a format of one frame of a downlinkcontrol channel CCH transmitted from each base station.

[0063] Referring to FIG. 2, one frame of a downlink signal from a basestation is configured with a start symbol SS, a preamble PR, a uniqueword UW, a data of control channel CCH, and an error checking bit CRC.

[0064] The data of control channel CCH can further be separated to aninformation bit for identifying the type of the base station and a datafor control channel CCH. More specifically, the information bit foridentifying the base station type is information identifying whether thebase station transmitting this downlink signal frame is an adaptivearray base station that controls downlink transmission directivity.

[0065] Note that the location of the identification information ismerely an example, and it can be inserted in the downlink transmissionsignal frame at any location.

[0066] Next, FIG. 3 is a timing diagram indicating a manner of signaltransmission/reception between a terminal and a base station accordingto the first embodiment of the present invention.

[0067] Referring to FIG. 3, when the base station to be connected is anadaptive array base station, information identifying an operation typeof the base station (a bit indicating that the base station is anadaptive array base station that performs downlink transmission control)is contained in control channel CCH of a downlink signal frame as shownin FIG. 2 and transmitted from the base station.

[0068] The terminal receiving it recognizes that the base station is anadaptive array base station and transmits a link channel LCH allocationrequest to the base station from a particular antenna among a pluralityof diversity reception antennas.

[0069] The adaptive array base station receives this uplink signal bythe adaptive array operation, and transmits an LCH allocationinstruction in the next frame by the adaptive array operation.

[0070] The terminal receives this LCH allocation instruction, which hasbeen transmitted from the base station with transmission directivity, atthe antenna that had transmitted the LCH allocation request in theprevious frame.

[0071] On reception, the terminal transmits an uplink synchronous burstto the base station from a particular antenna among a plurality ofdiversity reception antennas.

[0072] The adaptive array base station receives this uplink synchronousburst by the adaptive array operation, and transmits a downlinksynchronous burst in the next frame by the adaptive array operation.

[0073] The terminal receives this downlink synchronous burst, which hasbeen transmitted from the base station with transmission directivity, atthe antenna that had transmitted the uplink synchronous burst in theprevious frame.

[0074] On reception, the terminal transmits a traffic channel TCHactivation process to the base station from a particular antenna among aplurality of diversity reception antennas.

[0075] The adaptive array base station receives this traffic channel TCHactivation process by the adaptive array operation, and transmits adownlink traffic channel TCH in the next frame by the adaptive arrayoperation.

[0076] The terminal receives this downlink traffic channel TCH, whichhas been transmitted from the base station with transmissiondirectivity, at the antenna that had transmitted the traffic channel TCHactivation process in the previous frame.

[0077]FIG. 4 is a functional block diagram showing a systemconfiguration of a terminal according to the first embodiment of thepresent invention for realizing above mentioned operation principle.

[0078] Referring to FIG. 4, two antennas 11, 12 are connected to twofixed terminals of antenna select switch 13, while a movable terminal ofswitch 13 is connected to a transmission/reception signal alternatingswitch 14.

[0079] To switch 14, a modulation circuit 15 and a demodulation circuit16 are connected. The output of demodulation circuit 16 is provided to adigital signal processor DSP 18.

[0080] The outputs of antennas 11, 12 are provided to a reception levelcomparing apparatus 17. The output of reception level comparingapparatus is likewise provided to DSP 18. The inside of DSP indicated bya broken line 18 shows processes realized with software by DSP infunctional blocks.

[0081] Specifically, the output of demodulation circuit 16 is providedto a base station type identifying apparatus 18 a, of which output isprovided to an antenna select switch control apparatus 18 b. The outputof reception level comparing apparatus 17 is likewise provided toantenna select switch control apparatus 18 b.

[0082] The output of antenna select switch control apparatus 18 b isprovided to a switch-controlled input of antenna select switch 13.

[0083] Now, detailed description is given on the operation of theterminal shown in FIG. 4. This terminal is capable of performingdiversity reception, and a normal diversity operation will be described.

[0084] First, in transmission, a signal from a signal source such as amicrophone that is not shown is modulated by modulation circuit 15 andprovided to the movable terminal of antenna select switch 13 via switch14.

[0085] An uplink signal is transmitted by one antenna that is selectedby this switch 13 from antennas 11, 12.

[0086] In reception, the reception levels of signals received atantennas 11, 12, respectively, are compared to each other by receptionlevel comparing apparatus 17, and the comparison result is provided toantenna select switch control apparatus 18 b. Control apparatus 18 bcontrols switch 13 to select the antenna output with larger receptionlevel.

[0087] The reception signal from selected one antenna is provided todemodulation circuit 16 via switch 14 and demodulated. The signal thusdemodulated is provided to a speaker or the like that is not shown to beplayed back. This is the usual diversity reception operation.

[0088] Next, FIG. 5 is a flow chart showing an operation according tothe first embodiment of the present invention that is executed withsoftware by DSP 18 in the terminal shown in FIG. 4.

[0089] First, a signal containing base station type information (e.g.,downlink control channel CCH) that is received from the base station ateither one of antennas 11, 12 is demodulated by demodulation circuit 16and received at DSP 18 (base station type identifying apparatus 18 a)(step S1).

[0090] Based on the received base station type information, DSP 18determines whether the base station is an adaptive array base station(step S2).

[0091] If the base station is determined to be an adaptive array basestation at step S2, then as described referring to FIGS. 1 and 3, DSP 18(antenna select switch control apparatus 18 b) sets a select operationof antenna select switch 13 to receive a downlink signal in the nextframe at the antenna used for transmitting an uplink signal in animmediately preceding frame (step S3).

[0092] The method for selecting an antenna for transmitting an uplinksignal is not specifically limited. For example, one possible method isto calculate the average reception level of several frames for eachantenna for using an antenna with the high value for transmission.

[0093] Though the immediately preceding frame in the first embodimentrefers to one preceding frame of 2.5 microseconds as determined in thePHS specification, the present invention is not limited to this period.

[0094] If the base station is determined not to be an adaptive arraybase station (the base station is a non-directivity base station notperforming downlink transmission directivity control) at step S2, DSP 18(antenna select switch control apparatus 18 b) sets the select operationof antenna select switch 13 to receive a downlink signal by the abovementioned diversity reception (step S4).

[0095] Note that, when the adaptive array base station is a spatialmultiplexing base station that is connected to a plurality of terminalsin a spatial multiplexing manner using the adaptive array technique, asdescribed referring to FIGS. 9A and 9B, the process in FIG. 5 can becarried out as well (see step S2 in FIG. 5).

[0096] As above, according to the first embodiment of the presentinvention, when a base station is determined to be an adaptive arraybase station (or a spatial multiplexing base station), by causing aterminal capable of performing diversity reception to stop performingdiversity reception, and to set the antenna used for transmission to beused for immediately following reception, an excellent reception withtransmission directivity from the base station is attained at theterminal, and consequently, the improvement of DU ratio can be attained.

[0097] [Second Embodiment]

[0098]FIG. 6 is a functional block diagram showing a systemconfiguration of a terminal according to a second embodiment of thepresent invention for realizing an operation principle of the presentinvention.

[0099] The terminal according to the second embodiment shown in FIG. 6is different from the terminal according to the first embodiment shownin FIG. 4 in the following aspect. In the first embodiment of FIG. 4,when connecting to an adaptive array base station, transmissiondirectivity of the base station is used effectively by receiving at thesame antenna of a terminal that is used in the transmission, whereas inthe second embodiment of FIG. 6, when connecting to an adaptive arraybase station, an attempt is made to remove an interference wave in adownlink signal by performing adaptive array reception at a terminal aswell.

[0100] In FIG. 6, the inside of DSP as indicated by a broken line 18shows the processes realized with software by DSP in functional blocks,and configured with a base station type identifying apparatus 18a, andadaptive array reception and diversity reception compliant receptionapparatus 18c. Antennas 11, 12, modulation circuit 15, demodulationcircuit 16, reception level comparing apparatus 17, and base stationtype identifying apparatus 18 a are connected to adaptive arrayreception and diversity reception compliant reception apparatus 18 c.

[0101] The terminal shown in FIG. 6 is a terminal capable of selectivelyperforming diversity reception and adaptive array reception by using aplurality of antennas. In other words, diversity reception and adaptivearray reception are selectively performed with software by adaptivearray reception and diversity reception compliant reception apparatus 18c.

[0102] The operation of diversity reception and adaptive array receptionis well known in the art, and can selectively be realized using DSP(software) easily.

[0103] Next, FIG. 7 is a flow chart showing an operation according tothe second embodiment executed with software by DSP 18 in the terminalshown in FIG. 6.

[0104] First, a signal containing base station type information (e.g.,downlink control channel CCH) received at either one of antennas 11, 12from the base station is demodulated by demodulation circuit 16 andreceived at DSP 18 (base station type identifying apparatus 18 a) (stepS1).

[0105] Based on the received base station type information, DSP 18determines whether the base station is an adaptive array base station(step S2).

[0106] If the base station is determined to be an adaptive array basestation at step S2, then DSP 18 (adaptive array reception and diversityreception compliant reception apparatus 18 c) sets the receptionoperation to receive a downlink signal in the next frame by adaptivearray operation (step S5).

[0107] If the base station is determined not to be an adaptive arraybase station (i.e., to be a non-directivity base station) at step S2,then DSP 18 (adaptive array reception and diversity reception compliantreception apparatus 18 c) sets the reception operation to receive adownlink signal by diversity reception or adaptive array reception (stepS6).

[0108] Note that, when the adaptive array base station is a spatialmultiplexing base station that is connected to a plurality of terminalsin a spatial multiplexing manner using adaptive array technique, asdescribed referring to FIGS. 9A and 9B, the processes in FIG. 7 can becarried out as well (see step S2 in FIG. 7).

[0109] As above, according to the second embodiment of the presentinvention, when a base station is determined to be an adaptive arraybase station (or a spatial multiplexing base station), by causing aterminal capable of performing adaptive array reception or diversityreception to stop performing diversity reception, and to set adaptivearray reception, an excellent reception without interference wave isattained at the terminal, and consequently, the improvement of DU ratiocan be attained.

[0110] Though in each embodiment above, description has been made on thecase in which adaptive array base station that performs spatialmultiplexing connection by adaptive array process is employed as aspatial multiplexing base station for connecting to a plurality ofterminals, the present invention can be applied to any base stationusing any processing technique other than adaptive array process, aslong as it is a base station enabling spatial multiplexing connectionwith downlink directivity control.

[0111] As above, according to the present invention, a terminal canrealize optimum reception method corresponding to an operation type of abase station (whether it is a base station performing downlinktransmission directivity control or not) to be connected, byautomatically selecting a reception operation of the terminal inaccordance with a type of the base station to be connected, anddegradation of reception performance at the terminal can be prevented.

[0112] Industrial Applicability

[0113] According to the present invention, since optimum receptionmethod is selected at a terminal in accordance with presence/absence ofa control of downlink transmission directivity of a base station, it iseffective for a mobile communication system involving a base stationperforming transmission directivity control.

1. A radio terminal apparatus in a mobile communication system, saidmobile communication system including a plurality of radio basestations, each of said plurality of radio base stations transmitting asignal containing information that identifies a type of the radio basestation, said radio terminal apparatus comprising: determination means(18 a) for receiving a signal from a radio base station to be connectedamong said plurality of radio base stations, and determining a type ofthe radio base station based on said information; and selection means(18 b, 18 c) for selecting a reception operation mode for receiving asignal from the radio base station in accordance with the determinedtype of the radio base station.
 2. A radio terminal apparatus capable ofperforming diversity reception using a plurality of antennas (11, 12) ina mobile communication system, said mobile communication systemincluding a plurality of radio base stations, each of said plurality ofradio base stations transmitting information that identifies whether theradio base station is a radio base station performing an adaptive arrayoperation with directivity, said radio terminal apparatus comprising:determination means (18 a) for receiving a signal from a radio basestation to be connected among said plurality of radio base stations, anddetermining whether the radio base station is a radio base stationperforming said adaptive array operation based on said information; andset means (18 b) for setting an antenna used for a signal transmissionto the radio base station among said plurality of antennas to be usedfor a signal reception from the radio base station that immediatelyfollows the signal transmission when the radio base station isdetermined to be a radio base station performing said adaptive arrayoperation, and for setting said plurality of antennas to be used forreceiving a signal from the radio base station by diversity receptionwhen the radio base station is determined to be a radio base station notperforming said adaptive array operation.
 3. A radio terminal apparatuscapable of selectively performing adaptive array reception or diversityreception using a plurality of antennas (11, 12) in a mobilecommunication system, said mobile communication system including aplurality of radio base stations, each of said plurality of radio basestations transmitting information that identifies whether the radio basestation is a radio base station performing an adaptive array operationwith directivity, said radio terminal apparatus comprising:determination means (18 a) for receiving a signal from a radio basestation to be connected among said plurality of radio base stations, anddetermining whether the radio base station is a radio base stationperforming said adaptive array operation based on said information; andset means (18 c) for setting said plurality of antennas to be used forreceiving a signal from the radio base station by adaptive arrayreception when the radio base station is determined to be a radio basestation performing said adaptive array operation, and for setting saidplurality of antennas to be used for receiving a signal from the radiobase station by diversity reception or adaptive array reception when theradio base station is determined to be a radio base station notperforming said adaptive array operation.
 4. A radio terminal apparatuscapable of performing diversity reception using a plurality of antennas(11, 12) in a mobile communication system, said mobile communicationsystem including a plurality of radio base stations, each of saidplurality of radio base stations transmitting information thatidentifies whether the radio base station is a radio base stationperforming a spatial multiplexing operation with directivity, said radioterminal apparatus comprising: determination means (18 a) for receivinga signal from a radio base station to be connected among said pluralityof radio base stations, and determining whether the radio base stationis a radio base station performing said spatial multiplexing operationbased on said information; and set means (18 b) for setting an antennaused for a signal transmission to the radio base station among saidplurality of antennas to be used for a signal reception from the radiobase station that immediately follows the signal transmission when theradio base station is determined to be a radio base station performingsaid spatial multiplexing operation, and for setting said plurality ofantennas to be used for receiving a signal from the radio base stationby diversity reception when the radio base station is determined to be aradio base station not performing said spatial multiplexing operation.5. A radio terminal apparatus capable of selectively performing adaptivearray reception or diversity reception using a plurality of antennas(11, 12) in a mobile communication system, said mobile communicationsystem including a plurality of radio base stations, each of saidplurality of radio base stations transmitting information thatidentifies whether the radio base station is a radio base stationperforming a spatial multiplexing operation with directivity, said radioterminal apparatus comprising: determination means (18 a) for receivinga signal from a radio base station to be connected among said pluralityof radio base stations, and determining whether the radio base stationis a radio base station performing said spatial multiplexing operationbased on said information; and set means (18 c) for setting saidplurality of antennas to be used for receiving a signal from the radiobase station by adaptive array reception when the radio base station isdetermined to be a radio base station performing said spatialmultiplexing operation, and for setting said plurality of antennas to beused for receiving a signal from the radio base station by diversityreception or adaptive array reception when the radio base station isdetermined to be a radio base station not performing said spatialmultiplexing operation.
 6. A reception operation control program forcontrolling a reception operation in a radio terminal apparatus in amobile communication system, said mobile communication system includinga plurality of radio base stations, each of said plurality of radio basestations transmitting a signal containing information that identifies atype of the radio base station, said reception operation control programbeing for causing a computer to execute: a determination step ofreceiving a signal from a radio base station to be connected among saidplurality of radio base stations, and determining a type of the radiobase station based on said information; and a selection step ofselecting a reception operation mode for receiving a signal from theradio base station in accordance with the determined type of the radiobase station.
 7. A reception operation control program for controlling areception operation in a radio terminal apparatus capable of performingdiversity reception using a plurality of antennas (11, 12) in a mobilecommunication system, said mobile communication system including aplurality of radio base stations, each of said plurality of radio basestations transmitting information that identifies whether the radio basestation is a radio base station performing an adaptive array operationwith directivity, said reception operation control program being forcausing a computer to execute: a determination step of receiving asignal from a radio base station to be connected among said plurality ofradio base stations, and determining whether the radio base station is aradio base station performing said adaptive array operation based onsaid information; and a set step of setting an antenna used for a signaltransmission to the radio base station among said plurality of antennasto be used for a signal reception from the radio base station thatimmediately follows the signal transmission when the radio base stationis determined to be a radio base station performing said adaptive arrayoperation, and for setting said plurality of antennas to be used forreceiving a signal from the radio base station by diversity receptionwhen the radio base station is determined to be a radio base station notperforming said adaptive array operation.
 8. A reception operationcontrol program for controlling a reception operation in a radioterminal apparatus capable of selectively performing adaptive arrayreception or diversity reception using a plurality of antennas (11, 12)in a mobile communication system, said mobile communication systemincluding a plurality of radio base stations, each of said plurality ofradio base stations transmitting information that identifies whether theradio base station is a radio base station performing an adaptive arrayoperation with directivity, said reception operation control programbeing for causing a computer to execute: a determination step ofreceiving a signal from a radio base station to be connected among saidplurality of radio base stations, and determining whether the radio basestation is a radio base station performing said adaptive array operationbased on said information; and a set step of setting said plurality ofantennas to be used for receiving a signal from the radio base stationby adaptive array reception when the radio base station is determined tobe a radio base station performing said adaptive array operation, andfor setting said plurality of antennas to be used for receiving a signalfrom the radio base station by diversity reception or adaptive arrayreception when the radio base station is determined to be a radio basestation not performing said adaptive array operation.
 9. A receptionoperation control program for controlling a reception operation in aradio terminal apparatus capable of performing diversity reception usinga plurality of antennas (11, 12) in a mobile communication system, saidmobile communication system including a plurality of radio basestations, each of said plurality of radio base stations transmittinginformation that identifies whether the radio base station is a radiobase station performing spatial multiplexing operation with directivity,said reception operation control program being for causing a computer toexecute: a determination step of receiving a signal from a radio basestation to be connected among said plurality of radio base stations, anddetermining whether the radio base station is a radio base stationperforming said spatial multiplexing operation based on saidinformation; and a set step of setting an antenna used for a signaltransmission to the radio base station among said plurality of antennasto be used for a signal reception from the radio base station thatimmediately follows the signal transmission when the radio base stationis determined to be a radio base station performing said spatialmultiplexing operation, and for setting said plurality of antennas to beused for receiving a signal from the radio base station by diversityreception when the radio base station is determined to be a radio basestation not performing said spatial multiplexing operation.
 10. Areception operation control program for controlling a receptionoperation in a radio terminal apparatus capable of selectivelyperforming adaptive array reception or diversity reception using aplurality of antennas (11, 12) in a mobile communication system, saidmobile communication system including a plurality of radio basestations, each of said plurality of radio base stations transmittinginformation that identifies whether the radio base station is a radiobase station performing a spatial multiplexing operation withdirectivity, said reception operation control program being for causinga computer to execute: a determination step of receiving a signal from aradio base station to be connected among said plurality of radio basestations, and determining whether the radio base station is a radio basestation performing said spatial multiplexing operation based on saidinformation; and a set step of setting said plurality of antennas to beused for receiving a signal from the radio base station by adaptivearray reception when the radio base station is determined to be a radiobase station performing said spatial multiplexing operation, and forsetting said plurality of antennas to be used for receiving a signalfrom the radio base station by diversity reception or adaptive arrayreception when the radio base station is determined to be a radio basestation not performing said spatial multiplexing operation.